a) Field of the Invention
The invention relates to a device for flaring out or necking pipes which bends the opening of the pipe wall outward in such a way that a neck is formed around the opening of the pipe wall and which has a body to be inserted into the interior of the pipe and a die which is movable radially to the direction of the pipe, the outer diameter of the die corresponding to the inner diameter of the desired neck.
b) Background Art
U.S. Pat. No. 2,910,897 shows a device for necking which is characterized by a body which is to be inserted into the interior of the pipe and has a supported turning lever. The die is located at one end of the turning lever and a radial force is applied to the other end so as to turn the lever in such a way that the die can be pushed radially outward. It is difficult to achieve the necessary penetrating force with this arrangement. Moreover, this tool construction does not support the pipe from the inside to prevent pinching and buckling.
U.S. Pat. No. 2,868,263 shows a two-part deforming tool which is to be inserted into the interior of the pipe and expanded by means of a cylindrical wedge. Deformation surfaces for necking the wall are located in one part of the tool. This tool also does not support the pipe from within during deformation. The tool is not suitable for producing necks of different sizes. It can also not be used to form necks whose diameters approximate or correspond to those of the pipe to be necked.
U.S. Pat. No. 2,983,167 shows a tool serving to produce very small necks, so-called nipples, at rigid-walled pipes. The deformation is only supported from the outside of the pipe by a relatively massive supporting construction. The deformation bayonets are evidently hydraulically actuated.
A common characteristic of these and other known methods consists in that the pipe tends to be pinched from the inside either laterally adjacent to the necking or at the back of the pipe on both sides of the necking during the necking process or branching of the pipe. This is primarily a phenomenon similar to buckling. This phenomenon also occurs when the outside of the pipe is provided with a rigid supporting casing or shell.